In order to be driven, electrically drivable tools require an electrical energy source, which may be inserted, for example, into a cavity of the tool. The tool may be an electrically drivable surgical tool such as, for instance, a surgical screwdriver. An exemplary surgical screwdriver having a receptacle for a battery or other electrical energy source is disclosed in the European patent application EP 14188180.5.
Since the energy source is generally a direct-current source, it is important that the energy source is correctly inserted and the electrical terminals are not reversed. This is because, otherwise, the tool might become permanently damaged. Such a polarity reversal protection is also required by the standard EN 60601. Measures for preventing polarity reversal per se are already known from the prior art:
DE 4 12 666 C describes terminal connections for batteries. These have main bodies and, extending therefrom, terminal contacts that are realized as tube stubs. These tube stubs of the positive and negative terminals may differ in diameter size. The tube stubs are arranged at one and the same end of the battery. Owing to this arrangement of the terminals, however, the batteries must be of a comparatively large width perpendicularly to their longitudinal axis. The cavity of the tool, and accordingly also the tool, must thus be dimensioned accordingly; so that the battery can be accommodated. In many cases this is disadvantageous, however, for example if the tool is a surgical, screwdriver that is intended to be held in one hand. Moreover, a series connection of a plurality of batteries is rendered considerably more difficult by this arrangement of the terminals.
According to DE 2 237 279 A1, a reliable change operation is to be achieved in that the two battery terminals are realized as mutually superimposed studs having differing diameter sizes. Here also, however, the space requirement, perpendicular to the longitudinal axis of the battery is comparatively large, and here also series connection of a plurality of batteries is rendered considerably more difficult.
Furthermore, DE 10 2009 001 611 A1; discloses a battery compartment for an external cardiac pacemaker. In one exemplary embodiment, a 9-volt block, having two battery terminals of differing diameter, is used. Here, the space requirement perpendicular to the longitudinal axis of the battery is likewise comparatively large, and series connection of a plurality of batteries is rendered considerably more difficult.
DE 36 41 927 A1 relates to a polarity reversal protection for tubular batteries. For this purpose, a stepped offset is provided, which projects into receptacles of the battery holder. The batteries themselves comprise only a single terminal, extending therefrom. In many cases, however, this allows only an inadequate polarity reversal protection, since only the dimensions of this one terminal (i.e., for example, the diameter and axial length thereof) can determine whether the battery can be inserted in two opposite orientations.
A further important requirement that arises particularly in the case of surgical tools is that of preventing the reuse of the energy source. To enable the tool to be sterilized after an operation, the energy source must first be removed from the tool, since otherwise it could be destroyed as a result of the aggressive sterilization conditions, for example in that it could leak, as a result of which the sterilizer could also become contaminated. Usual energy sources can easily be inserted into the tool for a second time following sterilization. In this way, the tool could be used with an already used, and therefore at least partly discharged, energy source. This risk exists, in particular, if it cannot be seen from the outside of the energy source whether it has already been used in a tool. If this is not noticed until during the next operation, this might result in delays and consequently also in detrimental consequences for the patient. This is because, in particular, there may be an intraoperative failure of the tool. In order that the “essential power features” according to the already mentioned standard EN 60601 can also be achieved, it is necessary to prevent the reuse of the energy source.
U.S. 2006/0117911 A1 discloses battery-operated surgical screwdrivers that are intended to be used once. However, special structural measures that prevent reuse of the battery are not disclosed.
U.S. Pat. No. 6,126,670 relates to disposable battery packs that can be connected to a surgical tool in order to drive the latter. The correct polarity is achieved by means of a stud that is arranged on the tool and that engages in a corresponding opening in the battery pack. This measure, however, is not effective in preventing the battery pack from being reused.
DE 20 2000 017 971 U1 relates to handles for surgical instruments. Arranged in the handle there is an accumulator battery, which can be removed from the handle following removal of a cover. However, this document also does not disclose any mechanism that prevents reinsertion of the accumulator battery. On the contrary, it is even stated that the accumulator can be reinserted in the cavity after the latter has been sterilized.
U.S. Pat. No. 4,309,067 has as subject-matter interfaces for mechanically and electrically connecting a battery pack to a tool, which are intended to enable the battery pack to be removed, insofar as possible, with one hand. This connection is effected by means of a closure that can be actuated via a release button, which extends through a slot. However, this document also does not disclose any mechanism that prevents the battery pack from being reinserted.
The document U.S. Pat. No. 6,257,351 likewise discloses a battery pack that can be releasably connected to a surgical instrument. Here also, however, there is no disclosure of any mechanism that prevents reinsertion of the battery pack.
EP 1 813 200 A2 discloses surgical instruments having a removable battery. In one embodiment, the instrument comprises a primary portion and a grip portion that can be releasably connected to the primary portion and that contains a battery. The grip portion has a break-off portion that, after the grip portion has been separated from the primary portion, remains on the latter, such that further assembly of the said parts is no longer possible. However, this does not prevent reuse of the battery itself.
Additionally disclosed is a further exemplary embodiment of an instrument that has a counter and a motor look. In a first variant of this further exemplary embodiment, the counter is realized and arranged in such a manner that the motor look is activated after the battery has been removed from the instrument a predefined number of times (for example twice). A second variant provides that the motor look is activated after the grip portion has been separated from the primary portion a predefined number of times (for example twice). Both variants, however, are structurally complex and also susceptible to faults.